accommodate Consul 1.14.0 gRPC changes

See:
 - Consul Connect sidecar proxies require additional configuration for gRPC-TLS listener - hashicorp/nomad#15360
 - client: accommodate Consul 1.14.0 gRPC and agent self changes - hashicorp/nomad#15309
 - consul: add client configuration for grpc_ca_file - hashicorp/nomad#15701
 - Fix issue where TLS configuration was ignored for unix sockets in consul connect envoy. - hashicorp/consul#15913
 - Envoy -> consul “upstream connect error or disconnect/reset before headers. reset reason: connection termination” - https://discuss.hashicorp.com/t/envoy-consul-upstream-connect-error-or-disconnect-reset-before-headers-reset-reason-connection-termination/48303

templates/base.hcl.j2

@@ -23,6 +23,7 @@ consul {
     # The address to the Consul agent.
     address = "{{ nomad_consul_address }}"
     ssl = {{ nomad_consul_ssl | bool | lower }}
+    grpc_ca_file = "{{ nomad_consul_ca_file }}"
     ca_file = "{{ nomad_consul_ca_file }}"
     cert_file = "{{ nomad_consul_cert_file }}"
     key_file = "{{ nomad_consul_key_file }}"